1. Field of the Invention
This invention relates to a device for adjusting the starting position of a belt-like photosensitive member for use in a transfer-type electrophotographic reproducing apparatus. More particularly, it relates to one in which the belt-like photosensitive member (hereinafter referred to as a photosensitive belt) has a joint portion, or seam, and is trained about rollers to form a photosensitive member unit, the unit being removably mounted in the main body of the reproducing apparatus.
2. Discussion of the Prior Art
In a transfer-type electrophotographic reproducing apparatus, the support of the photosensitive member is generally classified into the drum type and the belt type, either of which is adapted to be withdrawn from the main body of the reproducing apparatus for maintenance of the photosensitive member. If a photosensitive belt has a joint, i.e., is not seamless, then it is imperative to locate this joint at a particular position at the time of commencement of reproduction, so that the joint cannot be included in an image area. On the other hand, if a drum type photosensitive member has a joint (or discontinuity), proper positioning of the joint is achieved with ease by merely providing a positioning pin on the drum shaft.
A difficulty has been encountered with the belt-type photosensitive member in that withdrawal of a roller shaft from the main body of the reproducing apparatus is difficult from the viewpoint of the mechanism. For this reason, a device has been proposed, (for example, Utility Model Application No. 48-135,998 filed in Japan in 1973 by the assignee of this application) in which a photosensitive belt and a roller shaft are integrally formed into a photosensitive member unit, and this unit is removably mounted in the main body of the reproducing apparatus with a gear train serving as a drive source, which gear train is incorporated in the main body. In that device, the photosensitive belt is adjusted so as to locate its joint at a particular position beforehand while the unit is outside the reproducing apparatus and then the unit is set in place in the main body of the reproducing apparatus. Another difficulty has been encountered with that device, however, in that because the roller shaft must be connected to a drive source by way of gears, at the time of such connection it frequently arises that the position of the joint is not in accord with the position of a reproduction sequence controlling mechanism, resulting in the necessity to readjust the position of the joint.
The present invention is directed to avoiding the above-mentioned difficulties.